1. Field of the Invention
The present disclosure relates to a method for manufacturing a gallium nitride wafer.
2. Description of the Related Art
A light emitting device (LED), which is a p-n junction diode having a characteristic of converting electrical energy into light energy, may be formed by compounding elements of a group III and a group IV in the periodic table. It is possible for a LED to achieve a variety of colors by adjusting compositional ratios of compound semiconductors.
Because of high thermal stability and wide bandgap energy, nitride semiconductors have been received great attentions in developing optical devices and high power density electronic devices. Particularly, blue, green and ultra violet (UV) light emitting devices or the like using nitride semiconductors are commercialized and being widely used.
According to typical technologies an ex-situ method using patterning or an in-situ method using a hydrochloric (HCl) gas is employed in order to grow a high-quality nitride semiconductor.
First, the ex-situ method through patterning includes an epitaxial lateral overgrowth (ELO) method and a pendeo epitaxy (PE) method or the like.
For example, in the ELO method, after growing a gallium nitride (GaN) thin film, a wafer on which the GaN thin film was grown is taken out from a reactor, and then put into a deposition equipment to form a silicon dioxide (SiO.sub.2) thin film on the GaN thin film. Thereafter, the wafer where the SiO.sub.2 thin film is deposited is taken out from the deposition equipment, and then a SiO.sub.2 mask pattern is formed using a photolithographic technique, and the GaN thin film is formed by putting the wafer back into the reactor.
Also, the PE method is also called as a maskless ELO method, and in the PE method, after growing GaN, a substrate is patterned by dry etching up to the substrate. If GaN is grown thereon again, GaN will not grow on the exposed substrate and a growth of GaN on the GaN will be predominant so that a high-quality GaN thin film can be obtained.
However, in the case of ELO, treading dislocations (TD) are propagated up to a top portion of a region without the mask pattern, which still causes the quality to be deteriorated. Also, manufacturing methods of ELO and PE according to a typical technology has disadvantages that complicated processes described above should be undergone and process time is also taken longer.
Meanwhile, in an etching method that uses an HCl gas to improve crystallinity of a GaN wafer, etch pits having an inverse pyramidal shape are formed by etching a dislocation region, and then a method of regrowing a nitride layer thereon is performed in-situ. However, HCl has less etching effect on a specific plane, for example {0001} plane, and has a disadvantage that the controlling of an etch shape and an etch density is difficult because an etching is done mainly on the region where dislocations are distributed.